Course I: First semester

Prof. S. D. Rathod Copy No III

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PHYLUM PORIFERA

(Pore bearing animals exhibiting multicellular organization)

1. Poriferans are pore bearing, multicellular animals since their body is porous due to

presence of ostia which are incurrent openings. The ex-current opening is a common,

single, large opening situated at the apex called osculum.

2. These are made-up of two germ layers an outer ectoderm and inner Endoderm; hence

known as diploblastic. There is a layer of matrix between these two cell layers which

contains different amoeboid cells performing different functions of connective tissue one

of those are archaeocytes. Archaeocytes play important role in repair and regeneration in

sponges.

3. Sponges are radially symmetrical.

4. Body Coelom is known as spongocoel which is lined internally by collar cells called as

choanocytes.

5. Sponges have canal systems are of three types namely, asconoid; syconoid and

leuconoid canal systems.

6. Sponges contain endoskeleton of spicules which are made up of either calcareous

material i.e. calcium carbonate or siliceous material i.e. silica.

L.S. of a Sponge

Course I: First semester

Prof. S. D. Rathod Copy No III

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Phylum Porifera is classified into three classes: 1. Calcaria; 2. Hexactinellida and 3.

Demospongia.

Class – Calcaria:

1. All sponges belonging to this class are marine, shallow water dwellers.

2. Their endoskeleton is made up of calcareous spicules.

3. They contain mostly asconoid type of canal system.

4. A typical example is Leucosolenia

Leucosolenia

1. This is tiny and colonial sponge found attached to

the rocks in the intertidal zone of the marine

waters.

2. Each individual is fingerlike, cylindrical or vase

shaped covered with numerous ostia.

3. There is a body cavity called spongocoel which

opens with a common excurrent opening called

osculum which is present at the apex.

4. Canal system is asconoid type.

Class – Hexactinellida:

1. All the sponges belonging to this class are marine, deep sea dwellers and mostly solitary.

2. Their endoskeleton is made up of siliceous spicules.

3. Due to siliceous spicules they are often referred as glass sponges.

4. They contain syconoid and leuconoid canal system.

5. A typical example is Euplectella

Course I: First semester

Prof. S. D. Rathod Copy No III

3

Euplectella

1. It is commonly known as Venus’s flower basket.

2. This is rare sponge found to a depth of about 1000 m

in the deep sea of Philippines and Japan.

3. It is solitary marine glass sponge and grows to about

15-30cm in length.

4. Osculum is closed due to sieve formation of fused

hexactinate spicules.

5. Entire skeleton is made up of fused hexactinate

spicules forming a lattice. It attaches to the

substratum with the help of tuft of root spicules.

Class – Demospongia:

1. Sponges belonging to this class are either marine or fresh water dwellers.

2. They are mostly shallow water forms and live organized and colonial.

3. Endoskeleton is made up of siliceous or calcareous spongine fibres which give them soft

texture.

4. Canal system is leuconoid type.

5. They are brightly colored and large in size.

6. Typical example is Euspongia (Bath sponge)

Euspongia (Bath sponge)

1. It occurs in warm waters of

Australia, America and

Mediterranean Sea; at a depth of

200m. 2. It is colonial and has a globular

compact brown colored body made

up of many individual. 3. Body covered with numerous ostia

and many oscula. Each osculum

represents an individual in a

colony. 4. It is unisexual usually female. It is called as bath sponge for its soft wooly spongine

fibres.

Osculum

Ostia

Root tuft